Auxiliary compressor in motor casing for controlling pressure therein



Dec. 19, 1967 P. A. WELLER ET AL 3,358,466

AUXILIARY COMPRESSOR IN MOTOR CASING FOR CONTROLLING PRESSURE THEREIN Filed April 25, 1966 2 Sheets-Sheet 1 (IQ T lzzzlenazs P575? 4. W544i? Ham/5 86 Dec. 19, 1967 WELLER ET AL 3,358,466

AUXILIARY COMPRESSOR IN MOTOR CASING FOR CONTROLLING PRESSURE THEREIN Filed April 25, 1966 2 Sheets-Sheet 2 United States Patent 3,358,466 AUXILiARY COMPRESSOR 1N MOTOR CASING FOR CONTROLLING PRESSURE TEEREEN Peter A. Welier, Farmington, and Hollis C. Grubb, Southfield, Mich, assignors to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed Apr. 25, 1966, Ser. No. 544,919 6 Claims. (Cl. 62-113 ABSTRACT OF THE DISCLOSURE T re invention provides means for cooling a dynamoelectric machine by injecting liquid refrigerant into the machine casing, contacting the interior surfaces of the machine with the refrigerant for cooling by evaporation, and then exhausting the evaporated refrigerant from the machine casing. A suction pump is provided within the machine casing. The pump has a fluid inlet communicating with the interior of the casing and a fluid outlet which extends exteriorly of the casing. The pump is actuated to exhaust refrigerant from the casing. This causes a reduction of the pressure within the casing to draw liquid refregerant from the source into the casing. The source of liquid refrigerant is preferably a condenser forming part of a refrigeration system. Normally, the pressure of the refrigerant within the condenser is sufiicient to cause flow from the condenser into the casing. However, there are times when the pressure iii the condenser is not sufiicient to cause fluid flow therefrom into the machine casing. At such times, the suction pump is actuated to result in drawing refrigerant from the condenser into the casing. Control means are provided to de-activate the suction pump during periods when the pressure within the condenser is sufiicient to cause flow from the condenser into the machine casing. In one embodiment, the refrigeration system of which the condenser forms a part includes an evaporator for receiving the exhaust refrigerant from the machine casing. Normal exhaust means are provided in addition to the suction pump outlet from the casing to the evaporator. These normal exhaust means are closed during periods when the suction pump is activated.

Background of the invention This invention relates to cooling dynamoelectric machines, and more particularly to cooling of a dynamoelectric machine through the agency of a refrigeration system wherein an auxiliary compressor pump is provided within the casing of the dynamoelectric machine to assist in circulation of refrigerant through the machine.

Various proposals have been made for the cooling of dynamoelectric machines by use of liquid regfrigerant. Generally, liquid refrigerant is taken from either the condenser or evaporator of a refrigeration system, circulated through the machine casing, and returned to a low pressure point in the refrigeration system, usually the evaporator. One problem which has been encountered in such cooling methods has been obtaining of proper pressure conditions for circulation of refrigerant from the refrigeration system through the machine casing.

When the liquid refrigerant is taken directly from the condneser of the refrigeration system, feeding of refrigerant from the condenser to the machine casing has been inadequate when low pressure conditions are present in the condenser. Low pressure conditions occur in the condenser at, for example, start up of the refrigeration system or in winter months when the water circulating through the condenser is very cold.

If it is desired to use the evaporator as a source of liquid refrigerant, some means must be provided to move the refrigerant from the evaporator to the machine casing because the pressure conditions within the evaporator are not such as to permit flow of regfrigerant from the evaporator to the machine casing without external pressure means being applied.

The present invention solves this problem by the provision of an auxiliary compressor pump directly within the machine casing. The auxiliary compressor pump'provides low pressure conditions within the machine casing. The low pressure in the casing may be used either to draw refrigerant from the condenser at times when the condenser pressure is unusually low or alternately to draw liquid refrigerant from the evaporator.

It is therefore an object of the present invention to provide a method for cooling dynamoelectric machines wherein an auxiliary compressor pump is provided within the machine casing to facilitate the flow of refrigerant either from the condenser of a refrigeration system or from the evaporator of a refrigeration system.

Another object of the invention is to provide such an auxiliary compressor pump which, when used in connection with the condenser, is caused to be inactive in the system at times when the condenser pressure is suflicient to cause flow of liquid refrigerant therefrom to the machine casing.

A still further object of the invention is to provide, in one embodiment, a system wherein liquid refrigerant is drawn from the condenser and flow control means are provided to automatically control the effect of the auxiliary compressor pump to result in this pump being effective only at such times as the condenser pressure is unusually low.

A further object of the invention is to provide, in another embodiment, flow control means which may be manually operated in order to control the functioning of the auxiliary compressor pump.

Another object of the invention is to provide an embodiment wherein liquid refrigerant is drawn directly from the evaporator by means of an auxiliary compressor pump and wherein no special valving means is necessary in order to control flow of refrigerant from the evaporator to the machine casing.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like re erence characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a diagrammetic view illustrating one embodiment of the invention wherein liquid refrigerant is drawn from the condenser to the machine casing during low pressure conditions in the condenser by means of an auxiliary compressor pump, and wherein flow control means are provided to eifectively take the auxiliary compressor pump out of the circuit when the pressure within the condenser is suificient to cause flow of liquid refrigerant therefrom to the machine casing;

FIGURE 2 is a diagrammetic view similar to FIGURE 1 illustrating an alternate circuit for feeding liquid refrigerant from the condenser through the machine casing; and

FIGURE 3 is a diagrammatic view wherein liquid refrigerant is drawn from the evaporator by means of an auxiliary compressor pump within the machine casing.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to he understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to FIGURE 1, there is shown a refrigeration system comprising an electric motor which drives, at one end, a centrifugal compressor 12 and, at the other end, an auxiliary compressor pump 14.

The compressor 12 draws vaporized refrigerant from an evaporator 16 through conduit 18. Hot compressed gas is then fed into a conduit 20. The conduit 29 discharges into a tube-type condenser 22.

Condensed refrigerant is discharged in liquid form from the condenser 22 to a sump 24. The sump 24 is connected to the evaporator 16 by means of a conduit 26. Flow is controlled from the sump 24 by means of a butterfly valve 28 which is provided with a float 30 to maintain the liquid level in the sump constant. This arrangement prevents condenser gases from entering conduit 26.

As thus far described, the system is substantially conventional. Referring now to the motor 10, it will be noted that the rotor 32 and stator 34 are sealed within casing 36. A conduit 38 leads from the casing 36 to the conduit 26 and thence to the sump 24. Liquid refrigerant is thus received from the sump 24 and injected into the casing 36. The refrigerant is completely or partially vaporized within the casing to cool the motor parts. The vaporized refrigerant is normally exhausted from the motor casing 36 by means of a conduit 46 which leads into connection with a conduit 42 and thence into the evaporator 16. The circuitry as thus far described is functional when the pressure in the condenser is sufiicient to cause effective flow of liquid refrigerant therefrom into the motor casing and thence back to the evaporator.

When the condenser pressure is unusually low, such as at start-up of the refrigeration system or during cold weather months when the condenser Water is at a relatively low temperature, auxiliary means must be utilized to draw refrigerant from the condenser to flow through the motor casing. The auxiliary means comprise the auxiliary compressor pump 14 which is of the centrifugal compressor-type. A conduit 44 leads from the connections of conduits 40 and 42 to the inlet of the pump 14. An exhaust conduit 46 leads from the outlet of the pump 14 to the condenser 22. A flow control device 43 is provided in the conduit 46 and a similar flow control device 50 is provided in the conduit 42. Each of the flow control devices may be, for example, a check valve.

During normal operation of the system, that is, when the condenser pressure is sufiicient to cause flow of refrigerant through the motor casing, the flow control device 48 is closed preventing fluid communication between the pump 14 and condenser 22. Similarly, during normal operation of the system, the flow control device 50 is open, permitting exhaust of refrigerant from the motor casing to the evaporator 16.

However, when the pressure within the condenser is near or below the pressure within the evaporator, it will be appreciated that some auxiliary means must be provided in order to maintain flow of refrigerant from the condenser and through the motor casing. At such times, the pump 14 acts to maintain the desired flow.

In operation, when condenser pressure drops to a sufficiently low value, the pump 14, which is connected to the bottom of the motor casing 36 by means of the conduits 40, 44, draws refrigerant, either liquid or vapor, from the bottom of the motor casing and thus reduces the pressure within the motor casing. It will be appreciated that when the condenser pressure is quite low, the pressure of the compressed gases discharged from the pump 14 will cause the flow control device 48 to open and permit communication between the pump 14 and condenser 22. Similarly, the low pressure conditions within conduits 40, 44 will cause the flow control device 50 to close, thus preventing drawing of refrigerant from the evaporator into the motor casing.

The low pressure conditions which are thus created within the motor casing 36 act, through the conduit 38, to draw liquid refrigerant from the condenser sump 24 to thus maintain flow of refrigerant through the motor cas- Contrariwise, when the condenser pressure is substantially above the evaporator pressure, the flow control device 48 will close to prevent back flow of condenser gas through the pump 14. As previously mentioned, the higher pressure conditions which then exist within the motor casing 36 cause the flow control device 50 to open and permit exhaust of refrigerant to the evaporator.

The pump 14 may either be connected directly to the rotor 32 as shown or it may have a separate drive. If connected to the rotor, it will run in a noflowstalled condition. If a separate drive is provided, the pump 14 may be deactivated during periods when it is not needed and operated only when necessary.

The embodiment illustrated in FIGURE 2 is a modified version of the FIGURE 1 embodiment and where appropriate, the same reference numerals have been used to identify the same components. In FIGURE 2, the lines 46 and 44 have been eliminated as well as the flow control devices 48, 50. In their place, a conduit 52 leads from the outlet of the pump 14 to the connection of the conduits 40, 42. The inlet to the pump 14 comprises a short conduit 54 which extends to the lower portion of the casing 36. A flow control device 56 is provided in conduit 52 and a flow control device 58 is provided in the conduit 40. The flow control devices 56, 58 are actuated either manually or by automatic power means, such as a solenoid, to the open and closed positions. 7

In the embodiment illustrated in FIGURE 2, refrigerant normally fiows from the condenser sump 24 through conduits 26, 38 into the motor casing 36 as previously described under normal pressure conditions withinthe condenser 22. Refrigerant is normally exhausted from the casing 36 via conduits 4t 42 to the evaporator 16. The flow control device 58 is maintained in the open position during normal operation of the system. The flow control device 56 is maintained in the closed position during the normal operation of the system so as to deactivate the pump 14.

When the pressure in the condenser 22 falls below that which is necessary to result in effective flow of refrigerant from the sump 24 to the motor 10, the valve 58 is closed and the valve 56 is opened. This cuts ofi? drainage through conduit 40 to the evaporator and opens communication between the outlet of the pump 14 and the evaporator:

16. Refrigerant, in either the vaporized or liquid form, is drawn through conduit 54 into the inlet'of the pump 14 and exhausted therefrom via the conduit 52 to the evaporator 16. This results in a low pressure condition being created within the casing 36 to thus draw liquid refrigerant from the sump 24 into the motor casing in the-desired manner to cool the motor parts.

The system illustrated in FIGURE 3 differs from that of FIGURES 1 and 2 primarily in that liquid refrigerant is drawn from the evaporator 16 rather than the condenser 22 for cooling the motor 10. Again, where appropriate, the same numerals have been used to designate the same component parts.

In the FIGURE 3 embodiment, there is no connection between the condenser sump and the motor 10. Liquid refrigerant is obtained from the lower portion of the evaporator 16 by means of a conduit 60 which is connected to the lower portion of the evaporator housing and extends into communication with the interior of the motor 10. It will be appreciated that in normal operation of the refrigeration system, there is a pool of refrigerant within the evaporator. This pool of refrigerant is splashed and otherwise made to contact the interior portion of the evaporator in order to cause cooling of liquid passing through the evaporator tubes 62. Another conduit 64 leads from the outlet of the pump 14 to the evaporator 16. The conduit 64 is preferably connected to the evaporator 16 at a point above the liquid level therein. A short conduit 66 leads from the inlet of the pump 14 to the lowermost portion of the motor casing 36.

In operation of the system in FIGURE 3, refrigerant is exhausted from the motor casing 36 via the conduit 66, pump 14 and conduit 64. The exhausting of refrigerant from within the motor casing 36 causes a low pressure condition within the casing. This low pressure condition causes liquid refrigerant to be drawn through the conduit 60 from the evaporator 16 and injected into the motor casing for cooling of the motor parts. The system of FIG- URE 3 is desirable from the standpoint that flow control mechanisms such as utilized in the FIGURES 1 and 2 embodiments are not necessary.

While the present invention has been described in connection with the cooling of the motor which drives the compressor of a refrigeration system, it will be appreciat'ed that the extended scope of the invention would include a motor or generator to be noted by the terminology dynamoelectric machine, positioned in an analogous manner with respect to the system as the compressor motor which is shown. Thus, refrigerant can be drawn from the system in the same manner to cool either an adjacent or remote dynamoelectric machine; it being understood, of course, that the compressor-condenser capacity of the system will be greater than that needed for the maximum cooling demand made upon the evaporator.

Having thus described our invention, we claim:

1. A method of cooling hermetic dynamoelectric machines by vaporizing liquid refrigerant brought into contact with hot machine surfaces, comprising the steps of providing a source of liquid refrigerant, connecting the source to the casing interior for fluid flow from the source into the casing, maintaining said source of liquid refrigerant under pressure normally sufficient to cause flow of liquid therefrom into the casing without resorting to reduction of pressure within the casing, reducing the pressure within the casing below the pressure source to draw liquid refrigerant from the source into the casing at such times when the pressure of the source of liquid refrigerant is insufficient to cause fluid flow from the source to the casing, and contacting the interior surfaces of the machine with the refrigerant for cooling by evaporation of liquid.

2. The method defined in claim 1 and further characterized in that the refrigerant is fed into the casing from the condenser of a refrigeration system, exhausting refrigerant from the casing into the evaporator of said refrigeration system, and reducing the pressure within the 5 casing only when the pressure within the condenser is substantially equal to the pressure within the evaporator.

31. A dynamoelectric machine and cooling means therefor, said machine including a rotor and stator enclosed Within a sealed casing, said cooling means comprising a source of liquid refrigerant, said source of liquid refrigerant being a condenser forming part of a refrigeration system, means connecting the interior of the machine casing to said source for liquid flow from the source into the casing, a suction pump within said machine casing, said pump having a fluid inlet communicating with the interior of said casing and a fluid outlet extending therefrom exteriorly of the casing, actuation of the pump being effective to exhaust refrigerant from the casing and thereby reduce the pressure within the casing sufiiciently to draw liquid refrigerant from the source into the casing, and control means effective to de-activate the suction pump during eriods when the pressure within the corn denser is suficient to cause fluid flow therefrom into the machine casing.

4. The structure defined in claim 3 and further characterized in that said refrigeration system includes an evaporator for receiving the exhaust refrigerant from said machine casing, normal exhaust means in addition to the suction pump outlet extending from the interior of the machine casing to the evaporator, and flow control means to close said normal exhaust means during periods when said suction pump is activated to exhaust refrigerant from the machine casing.

5. Structure as claimed in claim 4 and further characterized in that the fluid outlet of the suction pump extends from the casing to the evaporator, and pump fiow control means in the fluid outlet of the pump, and means to close said pump flow control means when the pump is deactivated and open said pump flow control means when said pump is activated.

6. A structure as claimed in claim 4 and further characterized in that the fluid outlet from the suction pump communicates with the interior of the condenser for exhausting refrigerant thereinto, pump flow control means in said fluid outlet, and means to close said pump flow control means when the pump is deactivated and to open said pump flow control means when the pump is activated.

References Cited UNITED STATES PATENTS 2,249,882 7/1941 Buchanan 62505 3,218,825 11/1965 McClure 62505 3,232,074 2/1966 Weller et a1 62-505 3,270,521 9/1966 Rayner et al 62505 LLOYD L. KING, Primary Examiner. 

1. A METHOD OF COOLING HERMETIC DYNAMOELECTRIC MACHINES BY VAPORIZING LIQUID REFRIGERANT BROUGH INTO CONTACT WITH HOT MACHINE SURFACES, COMPRISING THE STEPS OF PROVIDING A SOURCE OF LIQUID REFRIGERANT, CONNECTING THE SOURCE TO THE CASING INTERIOR FOR FLUID FLOW FROM THE SOURCE INTO THE CASING, MAINTAINING SAID SOURCE OF LIQUID REFRIGERANT UNDER PRESSURE NORMALLY SUFFICIENT TO CAUSE FLOW OF LIQUID THEREFROM INTO THE CASING WITHOUT RESORTING TO REDUCTION OF PRESSURE WITHIN THE CASING, REDUCING THE PRESSURE WITHIN THE CASING BELOW THE PRESSURE SOURCE TO DRAW LIQUID REFRIGERANT FROM THE SOURCE INTO THE CASING AT SUCH TIMES WHEN THE PRESSURE OF THE SOURCE OF LIQUID REFRIGER- 